Start near the end of the story and use a really good sentence to start it off. That way, you can build backwards as you write forwards. For example, you want to write a story about the end of a relationship. Decide if it is a good break up or not. Decide if it is a friendship, romantic relationship or familial. For each character, decide on who they are (you can always change it). Give them good names that give a clue to who they are.
Example: You could name the first person a woman falls in love with "Adam." This gives lots of clues.
A sentence you could use to start a story about a bad break up is this: Adam realized with the way the apartment looked that he would not be happy with Lilly's chaotic disorder.
A story of only six to nine hundred words is considered a short-short story. You can look up short-short stories on Google and read a lot of them. This might help you get in the right mood.
I have only one suggestion for a story that you might find fairly easy to write at this time. A high school girl has to write a short story. The deadline is the very next day. She is going slightly crazy trying to think up a plot for a story, but she is suffering from writer's block. She is thinking about everything else in the world except the plot for her story. In the end she falls asleep. The next morning she goes to school wondering what she is going to tell the teacher. When she gets to her class she is delighted to find that the class is being taken over by a substitute because her teacher has the flu. The substitute doesn't know anything about the assignments and just decides to read to the class for one hour. You might end the story with the beginning of a quote from a famous work of literature, such as, "It was the best of times, it was the worst of times . . . " and end with three dots like that. You might title your story: "The Dog Ate My Homework."
If it is purely fictional creative writing, then I would suggest going with something you are passionate about, developing an alter ego, and taking the character on an adventure you wouldn't have the opportunity to experience. Creative writing gives you the chance to create a world you only wish you could live in, free from the judgement and stereotypes of reality. Write to entertain yourself, as much as the reader. Take yourself on a journey and the audience will follow.